Abstract

The impact of Higher-Order Mode content on beam quality in large mode area fibers supporting several guided modes is carefully investigated. It is shown that even excellent beam quality (M2 < 1.1) in LMA fibers does not guarantee low HOM content, and that the presence of HOMs can lead to significant uncontrollable changes in beam quality, peak intensity, and pointing uncertainty that depend on the uncontrollable relative phase of the modes in the fiber.

M2 for different LP01-LP11 superpositions. (a) shows M2 as a function of LP11 fraction for the two limiting-case relative modal phases, and (b) shows M2 as a function of relative phase for a range of LP11 fractions.

Position of the near- and far-field centroids of the intensity pattern as a function of relative modal phase for different LP01-LP11 superpositions. The different curves in each graph represent different LP11 fractions.

(1.37 MB) Movie showing how the far-field intensity pattern changes with LP01-LP11 relative modal phase for 30% LP11 fraction. M2 remains good in all cases (between 1.08 and 1.35), although the peak intensity changes by 50% and the position of the centroid moves by nearly a beam radius. [Media 1]